Air seeders of this type have generally used either a knife or a cutting sweep which is carried at each of the seeding elements by the frame so as to cut a furrow in the ground into which the seeds are deposited. The depth of seeding is of fundamental importance to the germination and must therefore be very accurately controlled. The seed must be properly placed a required spacing from the soil surface and also taking into account soil surface moisture characteristics and the sub-surface moisture to obtain the optimum germination.
At the same time as the seeding process, it is highly desirable to effect banding of a fertilizer material so that the fertilizer is located adjacent to but spaced from the seeds so that once germination has occurred the roots can access the fertilizer. It is common therefore to provide a second duct on the seeding element for transportation of fertilizer to a position adjacent to but spaced from the seeds. It is undesirable to place the fertilizer directly with the seeds due to the chemical burning effect which can be obtained.
In many air seeders the depth of seeding is controlled by mounting the seeding element in fixed position on the frame and then by controlling the height of the frame relative to the ground as accurately as possible by providing a frame which can flex at different positions so the height of the frame varies to follow as accurately as possible the contours of the ground. However this approach has of course its limitations in that the frame necessarily must have some structural stability which thus limits its ability to totally follow the contours of the ground. Thus some of the seeding elements will at various times provide a depth of seeding which is too deep and other times the depth will be too shallow.
Attempts have been made to develop seeding systems in which the seeding elements are individually mounted upon the frame so that they can individually follow the contours of the ground.
One example of an arrangement of this type is shown in U.S. Pat. No. 4,417,530 (Kopecky) which shows a seeding element mounted upon a fixed tool bar with the seeding element being free to move up and down, the depth of the seeding being controlled by engagement of the packer wheel with the ground behind the seeding action.
Another example of an arrangement of this type is shown in U.S. Pat. No. 4,311,104 (Steilen) which shows a parallelogram linkage arrangement in which again the depth of seeding is controlled by the rolling action of a trailing packer wheel.
An older U.S. Pat. No. 2,357,730 (Peacock) discloses a similar arrangement in which fertilizer is deposited into a centre part of a furrow and seeds are deposited in two rows on either side of the centre part of the furrow through a second seeding element. Again the depth of the seeding action is controlled by a packer wheel.
In more recent years Halford in his U.S. Pat. No. 4,762,075 has provided an arrangement of this general type which is designed particularly for use in a "no-till" farming system in that the cutting action is effected by a narrow knife thus avoiding disturbing soil on either side of the seeding and fertilizing action.
In addition in a recent development Hiniker has disclosed in their brochure for their machine known as "6150 Sweep Feeder" an arrangement similar to the patent of Peacock in which there is a forward cutting knife depositing fertilizer and the subsequent double row feeding shank which deposits two row of seeds behind the fertilizer knife. Hiniker have provided two parallel packer wheels in place of the single wide packer wheel of Peacock. Hiniker have also provided a coulter which is positioned just in front of the fertilizer knife and is stated to be an independent depth gauge coulter which cuts through residue and maintains precise seed placement depth. It is understood therefore that the coulter provides an independent initial cutting action on the soil so as to avoid the remaining crop residue in a "no till" operation from interfering with the proper depth control provided by the conventional arrangement of the packer wheel and cutting knife assembly.
It is believed that the above examples are all heading in the right direction in providing a seeding action which can be effected in relatively heavy crop residue necessary in a no till operation while providing better control over the depth of the seeding action. However there remains opportunity for significant improvements in this field.